1. Field of the Invention
The present invention relates to a high-frequency semiconductor device that includes a cavity having a space and semiconductor elements contained in the cavity.
2. Description of the Related Art
It is increasingly demanded that semiconductor devices be designed to operate at larger power in, for example, microwave communication. The recent trend is therefore to use larger microwave semiconductor chips and more number of chips in combination. As a result, the cavity containing these chips has become larger. The cut-off frequency, which is determined by the length of cavity in the direction of the orthogonal to the microwave-propagation direction, must be kept at a higher frequency than operating frequencies. The decrease in the cut-off frequency degrades the isolation from the output side to the input side.
A semiconductor device is known, which is designed to prevent such degradation of the (see Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 5-83010, FIG. 1). As shown in FIG. 1, the cavity of this device is portioned by a grounding conductor, thereby to avoid characteristic degradation such as a decrease in the cut-off frequency. The cavity of this device has length a1, width b1 and height c1 (not shown). That is, this conventional semiconductor device has a plurality of semiconductor elements arranged in the widthwise direction.
This configuration, wherein semiconductor elements are arranged in the widthwise direction, has a problem in respect of radiation of heat because it operates at large power. More precisely, heat cannot be well radiated from the back of the device since many semiconductor elements are arranged in the device package having a small width and inevitably lie close to each other.
Further, gaps are likely to develop between the package cover and the partition walls provided in the package. Such gaps will degrade the device characteristics. This is one of the causes of the decrease in the device productivity.